Wow. Spent 2 years there driving on and around them (never drove on Bonneville itself, just some of the outlying flats) , and always thought they were solid salt all the way through!
Maybe that explains why the transportation department ran out of road salt back in the early 80s! Always thought that was so funny considering the salt flats and Morton salt being there, but hey.... it did make the news back then!

That place is mucky-soggy and horrible most of the year. Only from late spring until MAYBE early fall does it firm up. Lots and lots of times you can see cars and mostly jeeps and stuff stuck out near there in the mud. NASTY mud. Can even see where people thought they were cool and drove off the interstate to play, and usually there is signs of getting towed out of it.

That place is mucky-soggy and horrible most of the year. Only from late spring until MAYBE early fall does it firm up. Lots and lots of times you can see cars and mostly jeeps and stuff stuck out near there in the mud. NASTY mud. Can even see where people thought they were cool and drove off the interstate to play, and usually there is signs of getting towed out of it.

Yeah.... Got me a letter of reprimand for trying to take a USAF truck out on it (and promptly sunk to its undercarriage)!
As Dugway was a chemical weapons testing grounds for decades, they always told us 'Never leave designated roads". No getting out of it when you had to call the shop and ask them to send something to pull you out! Everyone at the facility knew exactly what had happened as the truck was driven back with all the salt n crap still clinging to it....